- /* UART Example for Teensy USB Development Board
- * http://www.pjrc.com/teensy/
- * Copyright (c) 2009 PJRC.COM, LLC
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
- // Version 1.0: Initial Release
- // Version 1.1: Add support for Teensy 2.0, minor optimizations
-
- #include <avr/io.h>
- #include <avr/interrupt.h>
-
- #include "uart.h"
-
- #if defined(__AVR_AT90USB162__) || defined(__AVR_ATmega16U2__) || defined(__AVR_ATmega32U2__) || defined(__AVR_ATmega16U4__) || defined(__AVR_ATmega32U4__) || defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB647__) || defined(__AVR_AT90USB1286__) || defined(__AVR_AT90USB1287__)
- # define UDRn UDR1
- # define UBRRnL UBRR1L
- # define UCSRnA UCSR1A
- # define UCSRnB UCSR1B
- # define UCSRnC UCSR1C
- # define U2Xn U2X1
- # define RXENn RXEN1
- # define TXENn TXEN1
- # define RXCIEn RXCIE1
- # define UCSZn1 UCSZ11
- # define UCSZn0 UCSZ10
- # define UDRIEn UDRIE1
- # define USARTn_UDRE_vect USART1_UDRE_vect
- # define USARTn_RX_vect USART1_RX_vect
- #elif defined(__AVR_ATmega32A__)
- # define UDRn UDR
- # define UBRRnL UBRRL
- # define UCSRnA UCSRA
- # define UCSRnB UCSRB
- # define UCSRnC UCSRC
- # define U2Xn U2X
- # define RXENn RXEN
- # define TXENn TXEN
- # define RXCIEn RXCIE
- # define UCSZn1 UCSZ1
- # define UCSZn0 UCSZ0
- # define UDRIEn UDRIE
- # define USARTn_UDRE_vect USART_UDRE_vect
- # define USARTn_RX_vect USART_RX_vect
- #elif defined(__AVR_ATmega328__) || defined(__AVR_ATmega328P__)
- # define UDRn UDR0
- # define UBRRnL UBRR0L
- # define UCSRnA UCSR0A
- # define UCSRnB UCSR0B
- # define UCSRnC UCSR0C
- # define U2Xn U2X0
- # define RXENn RXEN0
- # define TXENn TXEN0
- # define RXCIEn RXCIE0
- # define UCSZn1 UCSZ01
- # define UCSZn0 UCSZ00
- # define UDRIEn UDRIE0
- # define USARTn_UDRE_vect USART_UDRE_vect
- # define USARTn_RX_vect USART_RX_vect
- #endif
-
- // These buffers may be any size from 2 to 256 bytes.
- #define RX_BUFFER_SIZE 64
- #define TX_BUFFER_SIZE 256
-
- static volatile uint8_t tx_buffer[TX_BUFFER_SIZE];
- static volatile uint8_t tx_buffer_head;
- static volatile uint8_t tx_buffer_tail;
- static volatile uint8_t rx_buffer[RX_BUFFER_SIZE];
- static volatile uint8_t rx_buffer_head;
- static volatile uint8_t rx_buffer_tail;
-
- // Initialize the UART
- void uart_init(uint32_t baud) {
- cli();
- UBRRnL = (F_CPU / 4 / baud - 1) / 2;
- UCSRnA = (1 << U2Xn);
- UCSRnB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn);
- UCSRnC = (1 << UCSZn1) | (1 << UCSZn0);
- tx_buffer_head = tx_buffer_tail = 0;
- rx_buffer_head = rx_buffer_tail = 0;
- sei();
- }
-
- // Transmit a byte
- void uart_write(uint8_t data) {
- uint8_t i;
-
- i = tx_buffer_head + 1;
- if (i >= TX_BUFFER_SIZE) i = 0;
- // return immediately to avoid deadlock when interrupt is disabled(called from ISR)
- if (tx_buffer_tail == i && (SREG & (1 << SREG_I)) == 0) return;
- while (tx_buffer_tail == i)
- ; // wait until space in buffer
- // cli();
- tx_buffer[i] = data;
- tx_buffer_head = i;
- UCSRnB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn) | (1 << UDRIEn);
- // sei();
- }
-
- // Receive a byte
- uint8_t uart_read(void) {
- uint8_t data, i;
-
- while (rx_buffer_head == rx_buffer_tail)
- ; // wait for character
- i = rx_buffer_tail + 1;
- if (i >= RX_BUFFER_SIZE) i = 0;
- data = rx_buffer[i];
- rx_buffer_tail = i;
- return data;
- }
-
- void uart_transmit(const uint8_t *data, uint16_t length) {
- for (uint16_t i = 0; i < length; i++) {
- uart_write(data[i]);
- }
- }
-
- void uart_receive(uint8_t *data, uint16_t length) {
- for (uint16_t i = 0; i < length; i++) {
- data[i] = uart_read();
- }
- }
-
- // Return whether the number of bytes waiting in the receive buffer is nonzero.
- // Call this before uart_read() to check if it will need
- // to wait for a byte to arrive.
- bool uart_available(void) {
- uint8_t head, tail;
-
- head = rx_buffer_head;
- tail = rx_buffer_tail;
- if (head >= tail) return (head - tail) > 0;
- return (RX_BUFFER_SIZE + head - tail) > 0;
- }
-
- // Transmit Interrupt
- ISR(USARTn_UDRE_vect) {
- uint8_t i;
-
- if (tx_buffer_head == tx_buffer_tail) {
- // buffer is empty, disable transmit interrupt
- UCSRnB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn);
- } else {
- i = tx_buffer_tail + 1;
- if (i >= TX_BUFFER_SIZE) i = 0;
- UDRn = tx_buffer[i];
- tx_buffer_tail = i;
- }
- }
-
- // Receive Interrupt
- ISR(USARTn_RX_vect) {
- uint8_t c, i;
-
- c = UDRn;
- i = rx_buffer_head + 1;
- if (i >= RX_BUFFER_SIZE) i = 0;
- if (i != rx_buffer_tail) {
- rx_buffer[i] = c;
- rx_buffer_head = i;
- }
- }
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